Compositions useful for polishing the surfaces of various work pieces are well known in the art. Conventional polishing compositions, which are used for polishing the surfaces of semiconductors, glass, crystal, metal and ceramic work pieces, generally comprise aqueous slurries of an appropriate abrasive agent or mixtures of such agents. Known abrasive agents include cerium oxide, aluminum oxide, zirconium oxide, tin oxide, silicon dioxide, titanium oxide, etc. Composition comprising such agents are generally used by first applying the composition to a polishing pad or to the surface to be polished. The polishing pad is then applied to the surface, which causes the abrasive particles contained within the composition to mechanically abrade the surface, thus effecting the polishing action. However, such conventional polishing compositions cannot produce the highly specular and planar surfaces required in semiconductor and microelectronic component technology. Moreover, conventional polishing compositions have demonstrated disadvantages, such as poor polishing rates and poor surface quality, in polishing other work pieces. For example, the surfaces of glass, metals, semiconductors, etc., polished with such compositions demonstrate various defects such as haze, stains, scratches, "orange peel", undulations, undercuts, mesas, etc.
Thus, attempts have been made to improve the efficiency and quality of polishing compositions. Two methods of attaining improvement in these areas have been directed to combining various abrasives and/or adding various adjuvants to the compositions.
Polishing compositions comprising specific combinations of abrasive particles are disclosed, e.g., in U.S. Pat. No. 4,601,755 which discloses polishing compositions comprising at least one crystalline phase of cerium oxide and a rare earth pyrosilicate. U.S. Pat. No. 4,786,325 discloses a glass polishing composition comprising ceric oxide and at least one oxide of a lanthanide or yttrium rare earth. Likewise, U.S. Pat. No. 4,769,073 discloses cerium-based polishing compositions for polishing organic glass surfaces which comprise ceric oxide, a cerous salt and optionally, pyrosilicates or silica.
Examples of the use of adjuvants in polishing compositions are disclosed, e.g., in U.S. Pat. No. 4,959,113 which discloses compositions useful for polishing metal surfaces which comprise water, an abrasive agent and a salt or a combination of salts to promote the polishing effectiveness of the metal surface by the abrasive agent. Similarly, U.S. Pat. No. 4,462,188 is directed to semiconductor polishing compositions which comprise a colloidal silica sol or gel, a water soluble amine and a water soluble quaternary ammonium salt or base. U.S. Pat. No. 4,588,421 discloses compositions useful for polishing silicon wafers comprising an aqueous colloidal silica solution gel and piperizine. It is disclosed that the addition of piperizine provides increased polishing efficiency among other benefits. U.S. Pat. No. 4,954,142 discloses methods for polishing electronic components comprising contacting the surface of the component with a slurry comprising abrasive particles, a transition metal chelated salt and a solvent. This patent further discloses that the abrasive particles may be any of those commonly used such as silica, ceria, alumina, silicon carbide, silicon nitride, ferric oxide, etc.
However, even with such combinations of abrasive agents and the addition of adjuvant materials, conventional polishing compositions cannot produce the planarized surfaces needed in modern semiconductor and microelectronics technology.
Preparation of semiconductors and other microelectronic components generally involves building many interconnected layers of components, which may include products like very large scale integrated circuits (VLSIC) and ultra large scale integrated circuits (ULSIC). Thus, compositions useful for polishing or planarizing semiconductors must be able to polish complex, anisotropic, composite surfaces which are comprised of multiple layers of interconnected high density integrated circuits both at and below the surface. In preparing semiconductors, the structure resulting from the interconnected layers of integrated circuitry is polished down to a predetermined planar level which may comprise components of varying size, shape and hardness, as well as trenches, holes and valleys of various depths and shapes. After such polishing, semiconductor preparation may continue by various other procedures, such as chemical vapor deposition, metalization via vapor deposition, photolithographic patterning, diffusion, etching, etc., as will be recognized by one skilled in the art.
To provide superior results, the composition used to polish or planarize the surface of the prepared semiconductor work piece must produce an extremely flat and level surface with a high quality polish, i.e., a planar surface. However, unlike conventional polishing, to provide a planar surface, the polishing action must be restricted to the level surface of the work piece and must not affect the topography, morphology and/or structures below that surface. Only such selective polishing action will produce the desired planar surface. Conventional polishing compositions are not suited for such procedures as they merely produce uneven, undulating surfaces by abrading certain regions on, below and within the surface of the work piece. It has proven difficult, if not impossible, to use conventional polishing products to obtain smooth defect-free surfaces wherein the polishing composition does not adversely effect the underlying structure of the work piece.
In these specialized fields of semiconductor and microelectronic component preparation, where layers of components are interconnected within tiny chips of silicon, ceramic or other insulator work pieces, extraordinarily planar surfaces are required at many levels. Otherwise, the function of the semiconductor or other device may be adversely affected to the point where it is worthless. Thus, the many microprocessing steps used to make such a device and the associated labor and equipment may be wasted by only one surface which may be defective because planarization techniques did not produce sufficiently planar surfaces.
Accordingly, it can be seen that there has been a long-felt need for compositions which provide improved polishing activity at improved rates, which will produce planar and defect-free surfaces, as well as methods for the use of such compositions. The present invention satisfies such long-felt need.